When the gain margin of the system is close to unity and the phase margin is close to zero then the system is?

When the gain margin of the system is close to unity and the phase margin is close to zero then the system is?

​If the gain margin is close to unity or the phase margin is close to zero, then the system is oscillatory.

Which of the following statement is correct for a system with gain margin close to unity of a phase margin close to zero?

Explanation: A system is relative stable not stable if the phase margin is close to zero then the stability is checked by gain margin.

What does gain margin tell you?

Defining the phase crossover frequency ω1 to be the frequency at which the phase angle of the open-loop transfer function equals −180° gives the gain margin Kg: For an unstable system, the gain margin indicates how much the gain must be decreased to make the system stable.

How much gain margin is enough?

In general, the phase margin of 30–60 degrees and the gain margin of 2–10 dB are desirable in the closed-loop system design. A system with a large gain margin and phase margin is stable but has a sluggish response, while the one with a small gain margin and phase margin has a less sluggish response but is oscillatory.

What is the Gain margin of a system when the magnitude of the polar plot at phase cross over is a?

Explanation: Gain margin of a polar plot passing through the critical point is zero.

What does the phase margin of a system specify?

Phase margin indicates relative stability, the tendency to oscillate during its damped response to an input change such as a step function. Gain margin indicates absolute stability and the degree to which the system will oscillate, without limit, given any disturbance.

What is the difference between open and closed loop systems?

The main difference between an open-loop system and a closed-loop system is that the closed-loop system has the ability to self-correct while the open-loop system doesn’t. Consequently, closed-loop systems are often called feedback control systems while open-loop systems are also known as non-feedback controls.

Why is gain margin important?

Gain margin indicates absolute stability and the degree to which the system will oscillate, without limit, given any disturbance. The output signals of all amplifiers exhibit a time delay when compared to their input signals. This delay causes a phase difference between the amplifier’s input and output signals.

What is gain in control system?

Gain is a proportional value that shows the relationship between the magnitude of the input to the magnitude of the output signal at steady state. Many systems contain a method by which the gain can be altered, providing more or less “power” to the system.

Why is gain margin negative?

A positive gain margin means how much the control system gain can be increased, while a negative gain gain margin means how much the control system gain can be reduced. Therefore, in response to various uncertainties, the control system should satisfy negative and positive gain margin and phase margin.

When the system gain is doubled the gain margin becomes?

Gain margin is nothing but the inverse of the gain. Hence if gain of open loop system is doubled, then the gain margin will becomes half.

What is the difference between gain margin and phase margin?

2.) Interpretation (for a good understanding): Phase margin PM is the additional loop phase which would be necessary to bring the closed-loop system to the stability limit. Gain margin is the additional loop gain which would be necessary to make the closed-loop unstable.

When is gain margin negative in a control system?

When the System/OLTF phase is -180° but System Magnitude >1 > 1. Thereby making Gain Margin negative. I was able to correlate a physical meaning to this condition as the same would lead to a positive feedback condition with Gain >1 > 1 thereby leading to Unbounded output and hence instability.

Which is closer to oscillation unity gain or phase shift?

This therefore gives us two metrics to decide how close to oscillation the system is. These are the phase shift at unity gain, and the gain at 180° phase shift. The first had better be below 180°, and the second had better be below 1.

When does over unity gain become positive feedback?

A system with over-unity gain will oscillate with positive feedback. Usually the intent is to stabilize a system by using negative feedback. However, if this is phase shifted by 180°, then it becomes positive feedback, and the system will oscillate.